红层风化速率的岩体结构控制机理研究

The rock mass weathering problems is a very important issue in the long-term safety evaluation of engineering buildings. In the past, people paied more attentions to the weathering rates of rock block rather than the rock mass. In fact, that the frequent exchange with the outside of material and energy of the structures as open or semi-open system will undoubtedly aggravate the development of rock weathering. Therefore, the weathering of rock mass is different from the weahtering of rock block essentially. To carry out the study of weathering of the rock mass is not only more realistic but also more scientific. The application is to carry out the study of the controlling mechanism of rock mass structure on the weathering rate of red bed based on the rock mass structure control theory, regarding the natural large caverns developed in the red bed, like Meiyuan, Lankeshan, Ziyundong and Dafoyandong, as the research objects. Field investigations, laboratory and field test combined with numerical simulations will be adopted to do the research work. The physical and mechanical characteristics of the red bed, quantitative description of rock mass structures will be done; the weathering modes and the rock mass structure control law with different scale will be studied to reveal the rock mass structure control mechanism; to quantify the weathering rate of rock mass considering both of the weathering rate of rock block and structures; to proposed a rock mass weathering prediction model considering the transfer rules of different scale weathering modes and then to put forward some suggestions to against the weathering.

岩体风化问题是工程建筑物长期安全性评价的一个十分重要的课题。以往，人们多关注于岩石的风化速率分析，而对岩体的风化问题（亦即结构面的影响）却关注很少。事实上，结构面作为一个开放或半开放系统，因与外界物质能量交换频繁，无疑会加剧岩体风化作用的发生发展。因此，开展岩体的风化作用研究，不仅与岩石风化研究有本质的区别，而且更加切合实际、更加科学。本项目基于岩体结构控制理论，以大佛岩洞、烂柯山洞、梅岩和紫云洞等红层内的天然大型洞室为研究对象开展系统研究：通过现场调查和室内外试验，结合数值仿真模拟，对洞室围岩物理力学特性及其结构面特征进行定量化研究，概化红层洞室围岩结构类型；研究红层不同尺度的风化模式及岩体结构控制规律，揭示其风化模式的岩体结构控制机理；综合考虑岩块风化速率和结构面风化速率，量化岩体风化速率；基于岩体结构控制下风化模式转化规律，提出岩体风化预测模型，并给出相应的防风化措施建议。

本项目基于岩体结构控制理论，通过现场调查、室内试验和数值模拟，对红层的风化速率、风化机理以及天生石梁（石拱）的稳定性进行了深入研究，提出了岩体的风化速率主控因素及定量化表征方法。通过对龙游石窟洞室围岩凿痕的风化测量，发现其风化速率呈非线性变化，且受环境影响显著；衢州南宗孔庙不同朝向的院墙风化速率的差异性表明光照强度是主要影响因素；对平遥古城古砖的风化机理和风化模式进行了系统研究，并提出了相应的防治措施；利用对应分析，提出了用于表征凝灰岩风化等级的五个化学因子，并在柯岩某崩塌剖面进行了应用；利用已压裂的岩样进行室内干湿循环试验，发现软弱结构面（裂隙、层面）是影响砂岩崩解性的主控因素，且砂岩的耐崩解性远小于砾岩，这种岩性的差异风化、地表水侵蚀和岩体结构控制了红层洞穴和石梁的成因；数值模拟结果表明，烂柯山稳定状况较好，但是随着拱足的应力集中和干湿交替造成的风化剥蚀，将会对其整体稳定性构成威胁，应重点对拱足进行防护。